A conflict exists in industrial trucks between providing the greatest possible stability and adaptability to uneven surfaces. Industrial trucks are also intended to be as stable as possible even in the case of high lift heights. It is also necessary for its chassis to be able to adapt to uneven surfaces.
Four-wheeled industrial trucks have previously been described in which the two rear wheels are connected by an oscillating rigid axle which is connected at a point (rotary bearing) to the industrial truck and/or the chassis of the industrial truck. Similar to a three-wheeled industrial truck, this results in a three-point support and static redundancy so that problems with uneven surfaces are avoided. A drawback is that it has a greater tendency to tip over than an industrial truck with a four-point support because the center of gravity is located closer to the lateral tilting edges. These lateral tilting edges extend through the load wheels and meet in the bearing point of the oscillating rigid axle.
Industrial trucks with an oscillating frame have also previously been described. A drawback of this oscillating frame is that it is cost-intensive and requires more constructional space due to its rear frame extensions. It is also complex to construct from a technical perspective in terms of strength.
Industrial trucks with a hydraulic compensation of the level of the load wheels have also previously been described. A drawback thereof is that the hydraulic compensation only functions on good surfaces, i.e., on relatively even surfaces. If uneven surfaces exist, too much oil must flow to and fro through relatively small cross sections between the cylinders. This results in distortion and fractures in the frame.